Regeneration after removal of healthy mandibular condyles has been observed in humans and primates. The process of regeneration is not completely understood and contributing factors have not been isolated. The proposed study will provide insight into the complex phenomenon of regeneration after condylectomy. This will be done by displacement of the mandible anteriorly thus preventing the posterior and inferior collapse observed after condylectomy. Displacement of the mandible with changed muscle action and skelettal adaptations is used in the human for treatment of facial growth discrepancies. The exact action of this applied force is not known. However, it may influence the mandibular condyle which is a main growth site in the mandible. The purpose of this study is twofold: 1. Identification of the importance of mandibular displacement in the process if mandibular condyle regeneration after condylectomy. 2. Determination of the role of the mandibular condyle in reacting to applied forces in the mandible. Bilateral condylectomies will be performed in growing monkeys. Half of these monkeys will receive an appliance to displace the mandible anteriorly. Identical appliances will be placed in monkeys without condylectomies. After one year all animals will be sacrificed. The evaluation methods include: Longitudinal radiographs, plaster casts, histological evaluation and electromyography combined with cinefluorography.